1. Field of the Invention
The present invention is directed to improved methods for treating cotton-containing fabrics with cellulase as well as to the fabrics produced from these methods. In particular, the improved methods of the present invention are directed to contacting cotton-containing fabrics with an aqueous solution containing a fungal cellulase composition which comprises a combination of exo-cellobiohydrolase I type components and endoglucanase components wherein the exo-cellobiohydrolase I type components are enriched relative to the endoglucanase type components. When the cotton-containing fabric is treated with such solutions, the resulting fabric possesses the expected enhancements in, for example, feel, appearance, and/or softening, etc., as compared to the fabric prior to treatment and the fabric also possesses reduced strength loss as compared to the fabric treated with a complete cellulase composition.
2. State of the Art
During or shortly after their manufacture, cotton-containing fabrics can be treated with cellulase in order to impart desirable properties to the fabric. For example, in the textile industry, cellulase has been used to improve the feel and/or appearance of cotton-containing fabrics, to remove surface fibers from cotton-containing knits, for imparting a stone washed appearance to cotton-containing denims and the like.
In particular, Japanese Patent Application Nos. 58-36217 and 58-54082, as well as Ohishi et al., "Reformation of Cotton Fabric by Cellulase", and JTN December 1988 journal article "What's New--Weight Loss Treatment to Soften the Touch of Cotton Fabric" each disclose that treatment of cotton-containing fabrics with cellulase results in an improved feel for the fabric. It is generally believed that this cellulase treatment removes cotton fuzzing and/or surface fibers which reduces the weight of the fabric. The combination of these effects imparts improved feel to the fabric, i.e., the fabric feels more like silk.
Additionally, it was heretofore known in the art to treat cotton-containing knitted fabrics with a cellulase solution under agitation and cascading conditions, for example, by use of a jet, for the purpose of removing broken fibers and threads common to these knitted fabrics. When so treated, buffers are generally not employed because they are believed to adversely affect dye shading with selected dyes.
It was still further heretofore known in the art to treat cotton-containing woven fabrics with a cellulase solution under agitation and cascading conditions. When so treated, the cotton-containing woven fabric possesses improved feel and appearance as compared to the fabric prior to treatment.
Lastly, it was also heretofore known that the treatment of cotton-containing dyed denim with cellulase solutions under agitating and cascading conditions, i.e., in a rotary drum washing machine, would impart a "stone washed" appearance to the denim.
A common problem associated with the treatment of such cotton-containing fabrics with a cellulase solution is that the treated fabrics exhibit significant strength loss as compared to the untreated fabric. Strength loss arises because the cellulase hydrolyzes cellulose (.beta.-1,4-glucan linkages) which, in turn, can result in a breakdown of a portion of the cotton polymer. As more and more cotton polymers are disrupted (broken down), the tensile strength of the fabric is reduced.
Because methods involving agitation and cascading of cellulase solutions over cotton woven fabrics require shorter reaction times, these methods are believed to provide cotton-containing woven fabrics of reduced strength loss as compared to cellulase treatment methods not involving agitation and cascading. In any event, such methods still nevertheless result in significant strength loss.
Accordingly, it would be particularly desirable to modify such cellulase treatment methods so as to provide reduced strength loss while still achieving the desired enhancements in the treated cotton-containing fabric arising from treatment with cellulase as compared to the fabric prior to treatment.
Additionally, because fungal sources of cellulase are known to secrete very large quantities of cellulase and further because fermentation procedures for such fungal sources as well as isolation and purification procedures for isolating the cellulase are well known in the art, it would be particularly advantageous to use such fungal cellulases in the methods for improving feel and/or appearance.